1. Field of the Invention
The present invention relates to an inspection system for inspecting efficiency of a filter, and more particularly to a gas mixing apparatus of an inspection system for inspecting efficiency of a filter.
2. Description of Related Art
Manufacturing of electronic devices are usually performed in clean rooms. This is mainly because if particles in a working environment attach to products during manufacturing, damages to the products are caused, thereby lowering yields of manufacturing and increasing manufacturing costs for manufacturers. Therefore, a number of the particles included in the environment of a manufacturing place of the electronic devices must comply with a certain standard, so as to lower chances of the particles attaching to the products. On the other hand, persons must wear clean suits in the clean room. The clean suits insulate particles on the persons or other contaminants from entering the clean room and causing contamination. Insulating effects of the clean suits are determined by a particle filtering efficiency of the clean suits. Hence, inspecting the particle filtering efficiency of the filters is an important issue in manufacturing of clean suits.
Generally, the particle filtering efficiency of the filter must comply with certain inspecting standards. For example, the Institut für Textil in Germany uses the VDI guideline 3926 type 2, which mainly performs inspecting using a method of loads of particles, as a basis, while the Institute of Environmental Sciences and Technology in America performs inspecting according to the IEST-RP-CC003.3 inspecting standard. Relating to inspecting methods and devices for inspecting the particle filtering efficiency of the filters, currently related patents such as Taiwan Patent No. 369598 and U.S. Pat. No. 5,255,716 have been presented. However, prior art inspecting technologies are not suitable for application in inspecting the particle filtering efficiency of the filter used in the clean rooms. This is mainly because an inspecting gas used has a particle concentration higher than a particle concentration in a clean indoor environment during inspecting, thereby being not in compliance with working environments of common clean rooms, causing inspecting results to be different from real situations.